A large volume of trash, including leaves, twigs, plastic or paper cups, cigarette butts, and wrappers, and the like, pass into storm drains adjacent to paved surfaces such as streets and parking lots, such as through curb inlets.
Larger spills of oil can also flow into storm drains, such as from loading docks, gas stations, and the like. In addition, quantities of oil or other hydrocarbons are frequently spilled on the ground and subsequent water flow, such as from rain, can cause the oil to flow into storm drains. This is referred to as "non-point-source pollution."
The volume of oil from non-point-source pollution in typical water runoff is surprisingly large. For example, a government study in one published article showed that storm water sampled from street sites contained an "event mean concentration" of 2.2 mg. of oil per liter of runoff water. Shepp, "Petroleum Hydrocarbon Concentrations Observed in Runoff from Discrete, Urbanized Automotive-Intensive Land Uses," Watershed 96. If one meter of rain per year falls on a street 10 meters wide, then at that observed mean rate, the annual runoff from each kilometer of street will contain about 275 liters of hydrocarbons. Moreover, other studies of non-point-source pollution have measured oil concentrations an order of magnitude higher at some locations. Spills can increase the volume of oil even more.
The result of such problems include enormous annual costs, both financial and environmental, by contaminating natural receiving waters.
Some known systems use a screen-type filter through which the water runoff passes. However, such systems are prone to becoming dogged with debris, thereby blocking the inlet to the storm drain. Also, such systems can collect only limited quantities of oil.
Other known systems use oil-absorbing materials, particularly cellulose-based ones, that can collect oil. However, those materials permit leaching of the absorbed oil back into the runoff water, because the absorbed oil is not encapsulated in the oil-absorbent material. In addition, those materials typically have small pores, creating a blocking effect that prevents long-term effectiveness in absorbing oil and limits the quantity of water runoff that can be passed through the material.
Other known systems are available for screening of oil runoff below grates, as in catchbasins. However, such systems are not suitable for the large number of curb-inlet storm drains that are installed already, and are continuing to be installed. Curb-inlet storm drains are used widely over catchbasins, in part because they suffer from fewer problems arising from the presence of standing water and residue sediments that are endemic to storm drains, and in part because they can handle high peak flows, such as during flash floods. Systems designed for screening oil runoff below grates or in catchbasins, therefore, are not generally suited to handle the problem of screening oil runoff into curb-inlet storm drains.
There has been a need for some time for trash and oil recovery systems for a curb inlet that would (1) contain oil quickly and permanently, (2) collect debris, (3) permit removal of trash and oil for disposal, and (4) permit collection over a long term and despite high peak flows.
Accordingly, it is a primary object of the present invention to achieve a more effective system for recovering trash and oil from water passing into curb-inlet storm drains or the like.
It is another object of the invention to provide an apparatus for effectively containing oil spills flowing into curb-inlet storm drains, over a wide range of flow rates.
It is another object of the invention to provide an apparatus for ameliorating oil spills by entrapping the oil in an oil-sorbent material.
It is another object of the invention to provide a means of improving the collection of spilled oil.
It is another object of the invention to provide collection systems that handle debris.
The present invention achieves the above and other objectives by use of a modular insert for curb-inlet storm drains having a composite collection system for trash and for oil or other hydrocarbons and related chemicals. A hopper contains a multitude of irregular, macroscopic fragments of a hydrophobic, compliant, oil-absorbent, copolymer material having high surface area. Preferably, the material is formed with a binder in a novel extrusion process. The fragments absorb and retain permanently a high quantity of oil and other chemicals passing through the hopper, while permitting a high water flow-through rate. The fragments are held in place by a removable bottom plate, which allows replacement of the filtering fragments, and an internal basket. Trash and debris are collected in the internal basket. The hopper is configured to be suspended in a storm drain adjacent to a curb inlet on a bracket and can be installed or serviced through a conventional manhole entry.
Other aspects of the invention will be appreciated by those skilled in the art after a reading of the detailed disclosure of the present invention below.